enable cos and sin on no_std builds

[wucke13]

Currently sin and cos functions are disabled on no_std. These are common functions which are easily available through libm, so it makes sense to expose them.

[iliekturtles]

They are currently disabled because the underlying implementations aren't available in core::f32 like they are in std::f32. Is there some way to use libm easily for no_std?

[adamreichold]

I think the libm crate can be used in no_std environments as it is a pure Rust reimplementation of MUSL's libm.

[wucke13]

Yes, further on there is a libm feature in num, which can be easily used since num is a dependency already

[wucke13]

@iliekturtles Any chance that you take you fix this?